Crystal meth is highly addictive and users develop tolerance quickly, needing more and more to get high. It can be snorted, smoked or injected, but swallowing is the safest method with the longest lasting effect. Although rare, this drug can cause seizures, strokes and heart attacks. Coming down can make the user tired, lethargic and depressed, making it tempting to do more of the drug which can lead to dependency. Users may become run-down and vulnerable to illnesses.